Json-schema to Protobuf Bug

[kequeen]

https://transform.tools/json-schema-to-protobuf

Automatically generated json-schema demo is wrong，it does't have any null type, and generate pb code is not check, so it's wrong too.

[marclipovsky]

@kequeen you'd probably want to file that against https://github.com/okdistribute/jsonschema-protobuf.